HDU 2899 Strange fuction

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cmath>
 4 #define sc(x) scanf("%d",&(x))
 5 #define sc1(x) scanf("%lf",&(x))
 6 #define pf(x) printf("%.4lf\n", x)
 7 using namespace std;
 8 int T;
 9 double y, front, rear, mid;
10 double r(double x)
11 {
12     return (42*pow(x, 6) + 48*pow(x, 5) + 21*pow(x, 2) + 10*x);
13 }
14 double f(double x)
15 {
16     return (6*pow(x, 7) + 8*pow(x, 6) + 7*pow(x, 3) + 5*pow(x, 2) - y*x);
17 }
18 double Find()
19 {
20     front = 0, rear = 100, mid;
21     while((rear - front) > 1e-6)
22     {
23         mid = (front + rear) / 2.0;
24         if(r(mid) < y)
25             front = mid + 1e-7;
26         else
27             rear = mid - 1e-7;
28     }
29     return (front + rear) / 2.0;
30 }
31 int main()
32 {
33     sc(T);
34     while(T--)
35     {
36         sc1(y);
37         if(r(100) > y)
38             pf(f(Find()));
39         else
40             pf(f(100));
41     }
42     return 0;
43 }